The present invention relates to a correction device for correcting the deviation of laser beams of the primary scanning direction used for an image forming apparatus. More particularly, the present invention relates to a correction device for correcting the deviation of laser beams of the primary scanning direction used for an image forming apparatus in which a plurality of beams of light simultaneously conduct scanning so that a plurality of lines can be simultaneously recorded, the correction device characterized in that: the deviation of beams of the primary scanning direction is detected; and an image forming position of each beam of light is corrected by a simple construction in accordance with the result of detection.
In an image forming apparatus, a laser beam modulated in accordance with an image signal is reflected on a rotational polygonal mirror so that the laser beam scans on a recording medium. In order to increase the recording speed in the above image forming apparatus, a plurality of laser beams are used and a plurality of lines are simultaneously recorded. The above construction is well known.
However, in the case where a plurality of laser beams simultaneously conduct scanning, the scanning position of the plurality of laser beams are deviated in the primary scanning direction. Accordingly, it is impossible to conduct image formation accurately and stably.
In order to solve the above problems, the following technique is disclosed in Japanese Patent Publication Open to Public Inspection No. 188713/1990:
Positions of a plurality of laser beams of the primary scanning direction is intentionally deviated beforehand, and a positional relation of the scanning position of each laser beam is investigated to be made clear. Then, a synchronization signal corresponding to each of the laser beams is generated, and recording operation of each laser beam is controlled in accordance with the corresponding synchronization signal.
However, when the positional relation between the scanning positions of laser beams has collapsed, it is difficult to obtain an accurate synchronization signal corresponding to each laser beam. Therefore, it is necessary to improve the mechanism by which a semiconductor laser is mounted, and further it is necessary to make the mount mechanism of heat resistant material so that the positional relation of the scanning position of a plurality of laser beams can be maintained. For this reason, the cost of the apparatus is increased.